Internal combustion engines are controlled in many different ways to provide acceptable driving comfort during all operating conditions. Some methods use engine output, or torque, control where the actual engine torque is controlled to a desired engine torque through an output adjusting device, such as with an electronic throttle, ignition timing, or various other devices.
Under some conditions, there is the potential for poor drivability when the vehicle operator releases and subsequently engages the accelerator pedal. Specifically, as described in U.S. Pat. No. 6,266,597, transmission or driveline gear lash crossing during such conditions can degrade driver feel. For example, when the engine transitions from exerting a positive torque to exerting a negative torque (or being driven), the gears in the transmission or driveline separate at the zero torque transition point. Then, after passing through the zero torque point, the gears again make contact to transfer torque. This series of events produces an impact, which if transmitted to the driver is called clunk, resulting in poor drivability and customer dissatisfaction.
This disadvantage of the prior art is exacerbated when the operator returns the accelerator pedal to a depressed position, indicating a desire for increased engine torque. In this situation, the zero torque transition point must again be traversed. However, in this situation, the engine is producing a larger amount of torque than during deceleration because the driver is requesting acceleration. Thus, another, more severe, impact is generally experienced due to the transmission or driveline lash during the zero torque transition.
As such, in U.S. Pat. No. 6,910,990, the system controls engine torque to transition through the transmission or driveline lash zone by limiting a rate of torque increase during such conditions. In other words, when near the transmission lash zone, engine torque is adjusted at a predetermined rate until the system passes through the transmission lash zone. Further, the limiting may be adjustable based on operating conditions. By varying the limitation on the torque change in this way, drivability can be improved.
However, the inventors herein have recognized a disadvantage with such an approach. In particular, while rate limiting torque changes may reduce clunk, it may also increase a response delay to the point noticeable by the driver. Further, the greater the reduction in clunk (i.e., the more torque increases or decreases are limited), the greater the response delay.
In this way, it may be possible to coordinate multiple torque actuators during a driver tip-in to both reduce clunk without substantially increasing total response time, while also providing improved operation for both slipping and non-slipping conditions. For example, by coordinating throttle and ignition timing adjustments during a driver tip-in in this way, it is possible to, in effect, increase pre-charging of the intake manifold and cylinders with airflow so that once the transition through the lash zone is complete, a more rapid torque increase is possible. As another example, by adjusting operating depending on whether slipping or non-slipping transmission conditions are present, it is possible to manage the lash transition for a fully locked transmission driveline.